1) if 4 khattas of land was sold by your father and uncle then in the partition suit partition should have been claimed for only 16 khattas
2) draw attention of the court to fact that preliminary decree should have been passed for only 16 khattas and not 20 khattas
3) advocate commisisoner report would reveal that only 16 khattas of land are available for partition
4) defendants can raise the question regarding sale
5) your case would not be dismissed but partition would be granted for only 16 khattas